By:Roderick Barrie, Emma Harrison-Trainor, Adrian Helmers and Fraser Smith
Introduction
A reaction is the behaviour of different chemicals as they interact. Colour change, production of heat, gas or light or the formation of precipitates indicate that a reaction has taken place. Reactions can occur at different rates.
The rate of reaction between any substances is determined by many different factors. These factors include concentration, temperature, and any catalysts involved in the reaction. Concentration is the percent ratio of the water compared to the chemical, the lower the percentage the lower the concentration of the chemical involved. Temperature can affect the rate of reaction depending on the extremes. A different temperature will either speed up or slow down the reaction rate of the chemicals involved. The final factor that will be examined, is the presence of catalysts. A Catalyst is a substance that initiates or accelerates a reaction, without actually being a reactant in the reaction.
In the following series of experiments, reaction rates will be measured and conclusions will be drawn. These conclusions will be compared to the circumstances in which the reaction has taken place which will prove and describe the above factors. Materials
Experiments
Materials: Chemical
Materials: Equipment
Materials: Safety
1 - Temperature
-3 Alka seltzer Tablets
-Hot water
-Cold water
-Water at room temperature
-3 beakers
-1 measuring cup
-1 thermometer
-1 stopwatch
Safety Precautions It is important to take the necessary precautions when handling chemicals as they can be very dangerous. Always wear safety goggles, and have any long hair tied back to avoid any accidents and always make sure to wash your hands after an experiment. When using the manganese dioxide and hydrogen peroxide in experiment three, be sure to remain a safe distance away from any open flames as the chemicals can explode. Experiment 1: Temperature Procedure 1) Place 250mL hot water into a beaker 2) Record the temperature 3) Place 1 Alka-Seltzer tablet in the hot water and record how long it takes to dissolve completely 4) Repeat steps 1-3 for room temperature and cold water 5) Record and compare results
Observations
WATER TYPE (exact temp.)
TIME FOR COMPLETE DISSOLVE
GENERAL OBSERVATIONS
Hot 62 degrees C
17.34 sec
Many large bubbles, fizzing sound
Room temperature 24 degrees C
52.24 sec
Many bubbles, gentle fizzing sound
Cold 6 degrees C
104.52 sec
Slow, very small bubbles
Sources of Error The temperatures recorded could be slightly out from the correct value possibly due to the length of time they were in the water. The thermometer may not have completely reached the level of the water before we took it out.However, due to the large difference in temperatures recorded, this small margin of error does not affect the experiment.Another possible error could be from being inconsistent in when we stopped the timer.We attempted to stop the timer exactly when we could not see the Alka-Seltzer tablet anymore.With all of the bubbles being created, it was sometimes hard to notice when the tablet fully disappeared.This also would not have major affect on our results as the times received were spread out. The beakers were placed on metal mesh heat pads over the ring tripod stand. Due to the fact that a Bunsen burner was used to heat the water, it is possible that the intense flame caused some of the water to be heated at an extremely rapid rate causing some loss of water. This means that there is a possibility that the results were not 100% accurate if water was lost in the process of heating the beaker. Although the amount of water in the beaker should not have affected the experiment the loss of water, if it happened, could have caused a comparison between different water levels. The second possible source of error, with the exception of human error, was the fact of temperature. Temperature decreases as an exponential function of time, therefore meaning that as our experiment continued on the temperature was decreasing for the test where the water was heated, and the temperature increased over time for the test where the water was cooled. Due to this change in temperature the temperatures we recorded the rates of reactions occurred at actually did not remain constant. Modifications to Procedure Originally, in the procedure for this experiment, we had requested that the student put only 25-50mL of water into the beakers in order to dissolve the tablets. After carrying out the experiment for the first time, we discovered that more water was needed in order for the tablet to dissolve as the solution became super saturated and would not allow the table to dissolve fully, which in turn changed the results. We changed the amount of water to 250mL to make sure that the tablet would fully dissolve. This amount of water in the beakers also made it easier to see that reaction taking place and to time it properly. Modifications to this Experiment To receive more accurate results we could conduct all three of the tests at the same time.This will make it easier to tell which reaction occurred faster.Also to receive more in depth results we could have conducted more experiments at other temperature levels.
Conclusion The observations from the experiment show that an Alka-Seltzer tablet dissolved completely after 17.34 seconds in hot water, 52.24 seconds in room temperature water and 104.52 seconds in cold water. In response to higher temperatures, particles begin to move more quickly. Once the particles are moving faster, collisions become more frequent then when the particles were moving more slowly. These collisions between particles occur in smaller amounts of time as they are happening faster and more frequently. Therefore temperature has a direct relationship with the rate of reaction in that the higher the temperature, the faster the reaction takes place. Experiment 2: Concentration Procedure Part A: 1) In the first beaker, place a tablespoon of baking soda 2) In the second beaker, mix together 10 mL of vinegar with 5 drops of water 3) Slowly pour the vinegar/water mixture into the beaker filled with baking soda 4) Observe and record the reaction results as well as the time taken for the reaction to occur Part B: 1) In a clean beaker, place a tablespoon of baking soda 2) In a second clean beaker, mix together 5 mL of water with 5mL of vinegar 3) Slowly pour the vinegar/water mixture into the beaker filled with baking soda 4) Observe and record the reaction results as well as the time taken for the reaction to occur Part C: 1) In a clean beaker, place a tablespoon of baking soda 2) In a second clean beaker, mix together 10 mL of water and 5 drops of vinegar 3) Slowly pour the vinegar/water mixture into the braker filled with baking soda 4) Observe and record the reaction results as well as the time taken for the reaction to occur -Compare results from Parts A, B and C Observations
Vinegar vs Water
Molarity
Time
Qualitative Observations
High Concentration 10 mL vinegar 5 drops of water
0.853 M
15.7 seconds
Bubbles Formed Fizzing No baking soda leftover
Medium Concentration 5 mL vinegar 5 mL water
0.4375 M
20.95 seconds
Less bubbles Less fizzing Some baking soda leftover
Low Concentration 5 drops of vinegar 10 mL water
0.0213 M
23.66 seconds
Even less bubbles Even less fizzing More baking soda leftover
Calculations Molarity = (Number of moles of solute) / (Volume of Solution (L)) = (Mass of solute sample/Molar mass of solute)/(Volume of Solution (L))
Density = Mass / Volume
Mass= (Density)x(Volume)
Molar Mass = Addition of Molar masses of the atoms in the molecule
5% vinegar = 5% acetic acid, 95% water Sources of Experimental Error Human errors could have been caused from improper measurement of the liquids.This would cause the molarities to be wrong, but this would not have a significant impact on the results.Also, the times that were taken could be out, as we attempted to stop the timer when we stopped seeing new bubbles being created.However, this observation is not the same each time even with the same reactants and products, so this observation is a little bit faulty.Also, the time it took to pour in the vinegar/water mixture slightly varied from each trial and this would cause the vinegar/water mixture to not reach the baking soda at all the same time.This would delay some bubbles from forming and delay our time result as well.These errors are small and they do not significantly affect the result of our experiment. Modifications to the Experiment To receive more accurate results, we could conduct all three tests at the same time.This would make it obvious which concentration reacted the fastest.Also, we could conduct more experimental trials.For example we could mix baking soda with a 3 mL water and 7 mL vinegar solution.This would further make our results more accurate and more in depth. Conclusion In this experiment solutions with higher concentrations are able to react in a smaller amount of time. Solutions having higher concentrations also have a faster rate of reaction, when compared to solutions with lower levels of concentration. Therefore it can be shown that rate of reaction has a direct relationship to the concentration as a higher concentration, results in faster rate of reaction. A solution with a higher concentration has more particles of the solute in the solution.These particles must react with the baking soda particles.If there are more of the vinegar particles, which there is in a high concentration solution, the chances of the vinegar particles coming in contact with the baking soda particles are greater. More of the particles collide, resulting in a faster reaction.The opposite is true for a weaker solution. Experiment 3: Catalyst Procedure Part A: 1) Fill Half of a clean test tube with hydrogen peroxide 2) Place a balloon on the top of the test tube 3) Record results Part B: 1) Fill half of a clean test tube with hydrogen peroxide 2) Add manganese Dioxide and quickly place a balloon on the top of the test tube 3) Record results - Compare results from Part A and B.
Observations
PRESENCE OF CATALYST
TIME
INFLATION OF BALLOON
GENERAL OBSERVATIONS
No Catalyst -just 5mL Hydrogen Peroxide
30 sec
Nothing
Balloon did not fill Nothing happened
Catalyst -Manganese Dioxide in 5mL Hydrogen Peroxide
5 sec
Slight inflation of balloon
Balloon went upright when attached to test tube, inflated slightly, then test tube started to get hot
10 sec
Production of heat
Sources of Experimental Error In this experiment, the time in which it takes to place the balloon on the test tube will vary, and in the process, some of the oxygen gas will escape. This could drastically change the results from the lab. Modifications to Procedure If we were to redo our lab, a modification we would add to the experiment would be to measure an exact mass of hydrogen peroxide and manganese dioxide, and to measure the size of the inflated balloon. By using exact masses and by measuring the inflation of the balloon, we would get a better idea of how much oxygen and water were produced. Conclusion When hydrogen peroxide was by itself, the balloon did not get inflated because no reaction took place. When MgO2 was added, the balloon inflated due to the pure oxygen that was produced. This is because MgO2 is a catalyst. A catalyst is a chemicals substance that changes the rate of reaction between other substances without being consumed in the reaction. It changes the minimum energy needed for a reaction to occur, enabling the reaction to take place at a lower temperature. In our lab, manganese dioxide allows hydrogen peroxide to decompose into oxygen gas and H2O by lowering the energy needed in the reaction: 2 H2O2 (aq) + MgO2 (s) → O2(g) + 2 H2O(l) + MgO2 (s)
Overall Conclusion From these experiments, we determined that temperature, concentration and catalysts affect the rate of reaction. The higher the temperature or concentration, the faster the rate of reaction will be. With the presence of a positive catalyst such as manganese dioxide, the rate of reaction will be faster. There are other factors which affect the rate of reaction however we did not perform experiments to demonstrate. These factors include negative catalysts, surface area, solvents, pressure, electromagnetic radiation, isotopes, order, stirring and even the intensity of light. Perhaps another way of improving our science experiment would be to include experimentation of more factors to truly understand the rate of the reactions which occur around us everyday.
Rates of Reaction
By:Roderick Barrie, Emma Harrison-Trainor, Adrian Helmers and Fraser SmithIntroduction
A reaction is the behaviour of different chemicals as they interact. Colour change, production of heat, gas or light or the formation of precipitates indicate that a reaction has taken place. Reactions can occur at different rates.
The rate of reaction between any substances is determined by many different factors. These factors include concentration, temperature, and any catalysts involved in the reaction. Concentration is the percent ratio of the water compared to the chemical, the lower the percentage the lower the concentration of the chemical involved. Temperature can affect the rate of reaction depending on the extremes. A different temperature will either speed up or slow down the reaction rate of the chemicals involved. The final factor that will be examined, is the presence of catalysts. A Catalyst is a substance that initiates or accelerates a reaction, without actually being a reactant in the reaction.
In the following series of experiments, reaction rates will be measured and conclusions will be drawn. These conclusions will be compared to the circumstances in which the reaction has taken place which will prove and describe the above factors.
Materials
-Hot water
-Cold water
-Water at room temperature
-1 measuring cup
-1 thermometer
-1 stopwatch
-Water
-Baking soda
-1 Dropper
-3 Measuring cups
-Measuring spoons
-1 Stopwatch
-3 stirring rods
-Hydrogen peroxide
-2 balloons
-1 stopwatch
Safety Precautions
It is important to take the necessary precautions when handling chemicals as they can be very dangerous. Always wear safety goggles, and have any long hair tied back to avoid any accidents and always make sure to wash your hands after an experiment. When using the manganese dioxide and hydrogen peroxide in experiment three, be sure to remain a safe distance away from any open flames as the chemicals can explode.
Experiment 1: Temperature
Procedure
1) Place 250mL hot water into a beaker
2) Record the temperature
3) Place 1 Alka-Seltzer tablet in the hot water and record how long it takes to dissolve completely
4) Repeat steps 1-3 for room temperature and cold water
5) Record and compare results
Observations
(exact temp.)
62 degrees C
24 degrees C
6 degrees C
Sources of Error
The temperatures recorded could be slightly out from the correct value possibly due to the length of time they were in the water. The thermometer may not have completely reached the level of the water before we took it out. However, due to the large difference in temperatures recorded, this small margin of error does not affect the experiment. Another possible error could be from being inconsistent in when we stopped the timer. We attempted to stop the timer exactly when we could not see the Alka-Seltzer tablet anymore. With all of the bubbles being created, it was sometimes hard to notice when the tablet fully disappeared. This also would not have major affect on our results as the times received were spread out.
The beakers were placed on metal mesh heat pads over the ring tripod stand. Due to the fact that a Bunsen burner was used to heat the water, it is possible that the intense flame caused some of the water to be heated at an extremely rapid rate causing some loss of water. This means that there is a possibility that the results were not 100% accurate if water was lost in the process of heating the beaker. Although the amount of water in the beaker should not have affected the experiment the loss of water, if it happened, could have caused a comparison between different water levels.
The second possible source of error, with the exception of human error, was the fact of temperature. Temperature decreases as an exponential function of time, therefore meaning that as our experiment continued on the temperature was decreasing for the test where the water was heated, and the temperature increased over time for the test where the water was cooled. Due to this change in temperature the temperatures we recorded the rates of reactions occurred at actually did not remain constant.
Modifications to Procedure
Originally, in the procedure for this experiment, we had requested that the student put only 25-50mL of water into the beakers in order to dissolve the tablets. After carrying out the experiment for the first time, we discovered that more water was needed in order for the tablet to dissolve as the solution became super saturated and would not allow the table to dissolve fully, which in turn changed the results. We changed the amount of water to 250mL to make sure that the tablet would fully dissolve. This amount of water in the beakers also made it easier to see that reaction taking place and to time it properly.
Modifications to this Experiment
To receive more accurate results we could conduct all three of the tests at the same time. This will make it easier to tell which reaction occurred faster. Also to receive more in depth results we could have conducted more experiments at other temperature levels.
Conclusion
The observations from the experiment show that an Alka-Seltzer tablet dissolved completely after 17.34 seconds in hot water, 52.24 seconds in room temperature water and 104.52 seconds in cold water. In response to higher temperatures, particles begin to move more quickly. Once the particles are moving faster, collisions become more frequent then when the particles were moving more slowly. These collisions between particles occur in smaller amounts of time as they are happening faster and more frequently. Therefore temperature has a direct relationship with the rate of reaction in that the higher the temperature, the faster the reaction takes place.
Experiment 2: Concentration
Procedure
Part A:
1) In the first beaker, place a tablespoon of baking soda
2) In the second beaker, mix together 10 mL of vinegar with 5 drops of water
3) Slowly pour the vinegar/water mixture into the beaker filled with baking soda
4) Observe and record the reaction results as well as the time taken for the reaction to occur
Part B:
1) In a clean beaker, place a tablespoon of baking soda
2) In a second clean beaker, mix together 5 mL of water with 5mL of vinegar
3) Slowly pour the vinegar/water mixture into the beaker filled with baking soda
4) Observe and record the reaction results as well as the time taken for the reaction to occur
Part C:
1) In a clean beaker, place a tablespoon of baking soda
2) In a second clean beaker, mix together 10 mL of water and 5 drops of vinegar
3) Slowly pour the vinegar/water mixture into the braker filled with baking soda
4) Observe and record the reaction results as well as the time taken for the reaction to occur
-Compare results from Parts A, B and C
Observations
10 mL vinegar
5 drops of water
Fizzing
No baking soda leftover
5 mL vinegar
5 mL water
Less fizzing
Some baking soda leftover
5 drops of vinegar
10 mL water
Even less fizzing
More baking soda leftover
Calculations
Molarity = (Number of moles of solute) / (Volume of Solution (L)) = (Mass of solute sample/Molar mass of solute)/(Volume of Solution (L))
Density = Mass / Volume
Mass= (Density)x(Volume)
Molar Mass = Addition of Molar masses of the atoms in the molecule
5% vinegar = 5% acetic acid, 95% water
Sources of Experimental Error
Human errors could have been caused from improper measurement of the liquids. This would cause the molarities to be wrong, but this would not have a significant impact on the results. Also, the times that were taken could be out, as we attempted to stop the timer when we stopped seeing new bubbles being created. However, this observation is not the same each time even with the same reactants and products, so this observation is a little bit faulty. Also, the time it took to pour in the vinegar/water mixture slightly varied from each trial and this would cause the vinegar/water mixture to not reach the baking soda at all the same time. This would delay some bubbles from forming and delay our time result as well. These errors are small and they do not significantly affect the result of our experiment.
Modifications to the Experiment
To receive more accurate results, we could conduct all three tests at the same time. This would make it obvious which concentration reacted the fastest. Also, we could conduct more experimental trials. For example we could mix baking soda with a 3 mL water and 7 mL vinegar solution. This would further make our results more accurate and more in depth.
Conclusion
In this experiment solutions with higher concentrations are able to react in a smaller amount of time. Solutions having higher concentrations also have a faster rate of reaction, when compared to solutions with lower levels of concentration. Therefore it can be shown that rate of reaction has a direct relationship to the concentration as a higher concentration, results in faster rate of reaction. A solution with a higher concentration has more particles of the solute in the solution. These particles must react with the baking soda particles. If there are more of the vinegar particles, which there is in a high concentration solution, the chances of the vinegar particles coming in contact with the baking soda particles are greater. More of the particles collide, resulting in a faster reaction. The opposite is true for a weaker solution.
Experiment 3: Catalyst
Procedure
Part A:
1) Fill Half of a clean test tube with hydrogen peroxide
2) Place a balloon on the top of the test tube
3) Record results
Part B:
1) Fill half of a clean test tube with hydrogen peroxide
2) Add manganese Dioxide and quickly place a balloon on the top of the test tube
3) Record results
- Compare results from Part A and B.
Observations
-just 5mL Hydrogen Peroxide
Nothing happened
-Manganese Dioxide in 5mL Hydrogen Peroxide
Sources of Experimental Error
In this experiment, the time in which it takes to place the balloon on the test tube will vary, and in the process, some of the oxygen gas will escape. This could drastically change the results from the lab.
Modifications to Procedure
If we were to redo our lab, a modification we would add to the experiment would be to measure an exact mass of hydrogen peroxide and manganese dioxide, and to measure the size of the inflated balloon. By using exact masses and by measuring the inflation of the balloon, we would get a better idea of how much oxygen and water were produced.
Conclusion
When hydrogen peroxide was by itself, the balloon did not get inflated because no reaction took place. When MgO2 was added, the balloon inflated due to the pure oxygen that was produced. This is because MgO2 is a catalyst. A catalyst is a chemicals substance that changes the rate of reaction between other substances without being consumed in the reaction. It changes the minimum energy needed for a reaction to occur, enabling the reaction to take place at a lower temperature. In our lab, manganese dioxide allows hydrogen peroxide to decompose into oxygen gas and H2O by lowering the energy needed in the reaction:
2 H2O2 (aq) + MgO2 (s) → O2(g) + 2 H2O(l) + MgO2 (s)
Overall Conclusion
From these experiments, we determined that temperature, concentration and catalysts affect the rate of reaction. The higher the temperature or concentration, the faster the rate of reaction will be. With the presence of a positive catalyst such as manganese dioxide, the rate of reaction will be faster.
There are other factors which affect the rate of reaction however we did not perform experiments to demonstrate. These factors include negative catalysts, surface area, solvents, pressure, electromagnetic radiation, isotopes, order, stirring and even the intensity of light.
Perhaps another way of improving our science experiment would be to include experimentation of more factors to truly understand the rate of the reactions which occur around us everyday.